全文获取类型
收费全文 | 4382篇 |
免费 | 458篇 |
国内免费 | 18篇 |
学科分类
医药卫生 | 4858篇 |
出版年
2019年 | 38篇 |
2018年 | 73篇 |
2016年 | 37篇 |
2015年 | 53篇 |
2014年 | 73篇 |
2013年 | 98篇 |
2012年 | 132篇 |
2011年 | 163篇 |
2010年 | 79篇 |
2009年 | 86篇 |
2008年 | 142篇 |
2007年 | 180篇 |
2006年 | 155篇 |
2005年 | 184篇 |
2004年 | 156篇 |
2003年 | 153篇 |
2002年 | 143篇 |
2001年 | 156篇 |
2000年 | 166篇 |
1999年 | 126篇 |
1998年 | 75篇 |
1997年 | 61篇 |
1996年 | 59篇 |
1995年 | 61篇 |
1994年 | 49篇 |
1993年 | 62篇 |
1992年 | 127篇 |
1991年 | 129篇 |
1990年 | 127篇 |
1989年 | 127篇 |
1988年 | 119篇 |
1987年 | 134篇 |
1986年 | 132篇 |
1985年 | 105篇 |
1984年 | 92篇 |
1983年 | 77篇 |
1982年 | 46篇 |
1981年 | 54篇 |
1980年 | 41篇 |
1979年 | 64篇 |
1978年 | 52篇 |
1977年 | 47篇 |
1976年 | 38篇 |
1975年 | 42篇 |
1974年 | 57篇 |
1973年 | 51篇 |
1971年 | 47篇 |
1970年 | 42篇 |
1968年 | 41篇 |
1966年 | 34篇 |
排序方式: 共有4858条查询结果,搜索用时 31 毫秒
1.
2.
3.
Joseph LeSauter Peter D. Balsam Eleanor H. Simpson Rae Silver 《The European journal of neuroscience》2020,51(1):71-81
Dopamine has been implicated in circadian timing underlying the food entrainable oscillator (FEO) circuitry and overexpression of the dopamine D2 receptor (D2R) in the striatum has been reported to reduce motivation to obtain food rewards in operant tasks. In the present study, we explored both of these mechanisms by examining food anticipatory activity (FAA) in dopamine D2 receptor‐overexpressing (D2R‐OE) mice under various durations of food availability. First, we noted that at baseline, there were no differences between D2R‐OE mice and their littermates in activity level, food intake, and body weight or in circadian activity. Under conditions of very restricted food availability (4 or 6 hr), both genotypes displayed FAA. In contrast, under 8‐hr food availability, control mice showed FAA, but D2R‐OE mice did not. Normalization of D2R by administration of doxycycline, a tetracycline analogue, rescued FAA under 8‐hr restricted food. We next tested for circadian regulation of FAA. When given ad libitum access to food, neither D2R‐OE nor controls were active during the daytime. However, after an interval of food restriction, all mice showed elevated locomotor activity at the time of previous food availability in the day, indicating circadian timing of anticipatory activity. In summary, motivation is reduced in D2R‐OE mice but circadian timing behavior is not affected. We conclude that an increase in striatal D2R reduces FAA by modulating motivation and not by acting on a clock mechanism. 相似文献
4.
5.
Catherine Nyangabyaki-Twesigye Michael Rugambwa Muhame Silver Bahendeka 《African health sciences》2015,15(4):1339-1341
Diabetes mellitus is a metabolic disease characterised by chronically high glucose levels. Genetic factors have been implicated in the aetiology following mutations in a single gene. An extremely rare form of diabetes mellitus is monogenic diabetes, a subset of which is permanent neonatal diabetes, and is usually suspected if a child is diagnosed with diabetes at less than 6 months of age.We present the first case reported from East Africa of a child diagnosed with permanent neonatal diabetes resulting from a mutation in the KCNJ11 gene encoding the Kir6.2 subunit.Despite the rarity of permanent neonatal diabetes, this diagnosis should be considered in infants with persistent hyperglycaemia requiring insulin therapy. Children with an ATP-sensitive potassium channel defect in the pancreatic beta cell have an overall good prognosis when treated with oral sulphonylurea therapy. 相似文献
6.
Timmy Le Cynthia L.Winham Fotis Andromidas Adam C.Silver Evan R.Jellison Aime A.Levesque Andrew O.Koob 《中国神经再生研究》2020,(10):1894-1902
Elevated levels of γ-synuclein(γ-syn)expression have been noted in the progression of glioblastomas,and also in the cerebrospinal fluid of patients diagnosed with neurodegenerative diseases.γ-Syn can be either internalized from the extracellular milieu or expressed endogenously by human cortical astrocytes.Internalizedγ-syn results in increased cellular proliferation,brain derived neurotrophic factor release and astroprotection.However,the function of endogenousγ-syn in primary astrocytes,and the relationship to these two opposing disease states are unknown.γ-Syn is expressed by astrocytes in the human cortex,and to gain a better understanding of the role of endogenous γ-syn,primary human cortical astrocytes were treated with chimera RNA interference(RNAi)targeting γ-syn after release from cell synchronization.Quantitative polymerase chain reaction analysis demonstrated an increase in endogenousγ-syn expression 48 hours after release from cell synchronization,while RNAi reduced γ-syn expression to control levels.Immunocytochemistry of Ki67 and 5-bromodeoxyuridine showed chimera RNAi γ-syn knockdown reduced cellular proliferation at 24 and 48 hours after release from cell synchronization.To further investigate the consequence of γ-syn knockdown on the astrocytic cell cycle,phosphorylated histone H3 pSer10(pHH3)and phosphorylated cyclin dependent kinase-2 pTyr15(pCDK2)levels were observed via western blot analysis.The results revealed an elevated expression of pHH3,but not pCDK2,indicating γ-syn knockdown leads to disruption of the cell cycle and chromosomal compaction after 48 hours.Subsequently,flow cytometry with propidium iodide determined that increases in apoptosis coincided with γ-syn knockdown.Therefore,γ-syn exerts its effect to allow normal astrocytic progression through the cell cycle,as evidenced by decreased proliferation marker expression,increased pHH3,and mitotic catastrophe after knockdown.In this study,we demonstrated that the knockdown of γ-syn within primary human cortical astrocytes using chimera RNAi leads to cell cycle disruption and apoptosis,indicating an essential role for γ-syn in regulating normal cell division in astrocytes.Therefore,disruption to γ-syn function would influence astrocytic proliferation,and could be an important contributor to neurological diseases. 相似文献
7.
Emily E. Spurlin Esther S. Han Elisabeth R. Silver Benjamin L. May Nicholas P. Tatonetti Myles A. Ingram Zhezhen Jin Chin Hur Arnold P. Advincula Hye-Chun Hur 《Journal of minimally invasive gynecology》2021,28(7):1411-1419.e1
Study ObjectiveThe purpose of this study was to assess the impact of the coronavirus disease 2019 (COVID-19) pandemic on surgical volume and emergency department (ED) consults across obstetrics-gynecology (OB-GYN) services at a New York City hospital.DesignRetrospective cohort study.SettingTertiary care academic medical center in New York City.PatientsWomen undergoing OB-GYN ED consults or surgeries between February 1, 2020 and April 15, 2020.InterventionsMarch 16 institutional moratorium on elective surgeries.Measurements and Main ResultsThe volume and types of surgeries and ED consults were compared before and after the COVID-19 moratorium. During the pandemic, the average weekly volume of ED consults and gynecology (GYN) surgeries decreased, whereas obstetric (OB) surgeries remained stable. The proportions of OB-GYN ED consults, GYN surgeries, and OB surgeries relative to all ED consults, all surgeries, and all labor and delivery patients were 1.87%, 13.8%, 54.6% in the pre–COVID-19 time frame (February 1–March 15) vs 1.53%, 21.3%, 79.7% in the COVID-19 time frame (March 16–April 15), representing no significant difference in proportions of OB-GYN ED consults (p = .464) and GYN surgeries (p = .310) before and during COVID-19, with a proportionate increase in OB surgeries (p <.002). The distribution of GYN surgical case types changed significantly during the pandemic with higher proportions of emergent surgeries for ectopic pregnancies, miscarriages, and concern for cancer (p <.001). Alternatively, the OB surgery distribution of case types remained relatively constant.ConclusionThis study highlights how the pandemic has affected the ways that patients in OB-GYN access and receive care. Institutional policies suspending elective surgeries during the pandemic decreased GYN surgical volume and affected the types of cases performed. This decrease was not appreciated for OB surgical volume, reflecting the nonelective and time-sensitive nature of obstetric care. A decrease in ED consults was noted during the pandemic begging the question “Where have all the emergencies gone?” Although the moratorium on elective procedures was necessary, “elective” GYN surgeries remain medically indicated to address symptoms such as pain and bleeding and to prevent serious medical sequelae such as severe anemia requiring transfusion. As we continue to battle COVID-19, we must not lose sight of those patients whose care has been deferred. 相似文献
8.
9.
10.
Active Commuting to School,Physical Activity,and Behavior Problems Among Third‐Grade Children 下载免费PDF全文
Mana Mann MD MPH Ellen J. Silver PhD Ruth E. K. Stein MD 《The Journal of school health》2018,88(10):734-743